This invention relates to turbochargers for internal combustion engines, and more particularly to diverters for divided volute turbochargers.
As explained, for example, in Price U.S. Pat. No. 4,395,884 and 4,474,006, many internal combustion engines are equipped with divided volute turbochargers. At high engine speeds, exhaust gas flows through both volutes of the turbocharger. In order to improve the efficiency of the turbocharger at lower engine speeds, however, one of the two volutes of the turbocharger is closed and all of the exhaust gas from the engine is diverted to the other volute. These modifications of the flow of exhaust gas through the turbocharger are effected by a so-called diverter associated with the turbocharger turbine.
As the Price patents point out, turbocharging not only improves engine efficiency during powering mode, it also improves the engine retarding efficiency of a compression relief type engine brake which may be associated with the engine. Because little or no fuel is being consumed during engine braking, the volume of exhaust gas from the engine is substantially diminished during compression relief engine braking. Turbocharger efficiency therefore tends to decline during engine braking even though the speed of the engine may be quite high. Thus exhaust gas flow rates during compression relief engine braking may be comparable to exhaust gas flow rates during low engine speed fueling mode operation. The Price patents therefore teach the use of a turbocharger diverter (for closing one turbocharger volute and diverting all exhaust from that volute to the other volute) during both low speed fueling mode and compression relief braking mode.
While the particular diverter mechanisms shown in the Price patent have worked extremely well, they are relatively large and require relatively large and strong actuator mechanisms. In particular, the Price diverters include a gate which must be pushed transversely across one volute or the exhaust gas passageway leading to one volute of the turbocharger. The fact that these gates move linearly has led to the use of in-line linear actuators, with the result that the entire diverter plus actuator mechanism is quite long transverse to the volute axis. In addition, the pressure of the exhaust gas on the gate means that there is typically considerable frictional resistance to motion of the gate. This means that a relatively large and strong actuator is required.
In view of the foregoing, it is an object of this invention to improve and simplify diverters for divided volute turbochargers.
It is a more particular object of this invention to provide divided volute turbocharger diverters which are more compact, more easily integrated into the turbocharger if desired, and easier to operate.